fn main() {
    {
        // 可以用use配合as给导入的函数起别名
        // 函数遮蔽，看起来就进原则依然适用
        use my::nested::say_hi as small_fn;
        small_fn();
    }
    say_hi();
}

fn say_hi() {
    println!("small fun");
}
mod my {
    pub mod nested {
        pub fn say_hi() {
            println!("hello")
        }
    }
}
